In recent years, flat-panel detection technologies develop drastically. Patent Document 1 describes a flat-panel detection technology which realizes the reduction of the cost of flat-panel detector, thereby the application of flat-panel detectors is popularized more rapidly and widely.
Flat-panel detection technologies may be divided into the following two types: direct detection and indirect detection. The key part of an indirect flat-panel detector is a flat-panel detector (FPD) for acquiring an image, which consists of the parts such as an X-ray conversion layer, a photodiode, a thin-film transistor, a signal storage basic pixel unit and a signal amplifying and reading unit, etc. The operating principle is as follows: an X-ray is converted into a visible light of about 550 nm via an X-ray conversion layer, the visible light is converted into an electrical signal via a photodiode, the electrical signal is stored in a signal storage unit by a thin-film transistor, and under the action of a driver circuit, the charges stored in a pixel unit is transferred to a read-out circuit, and the read-out circuit will further process the electrical signal, for example, amplify and perform analog-digital conversion on the electrical signal, and finally obtain the image information.
The amorphous silicon thin film in a photodiode has a photo-degeneration effect, which causes the photoelectric conversion efficiency of the photodiode to decrease after long-time illumination. Decreasing the thickness of the amorphous silicon thin film is helpful to reduce the photo-degeneration problem; however, when the thickness of the amorphous silicon thin film is decreased, the incident light will not be fully absorbed, and a large amount of light will penetrate the photodiode element, thus the conversion efficiency of the photodiode will be lowered. Therefore, it has become an important problem to be solved in the designing and manufacturing field of X-ray flat-panel detectors to control the thickness of the amorphous silicon thin film in a photodiode, reduce the photo-degeneration effect, and at the same time, increase the absorption efficiency and the photoelectric conversion efficiency of the photodiode on the incident light and thus increase the quantum detection efficiency of a ray detector.